Newton’s Laws of Motion Lab Questions Answer Key
- Describe all of the forces acting on the marble/ball as it rolls down the ruler. Explain how each of these affects the marble’s acceleration.
Answer: Gravity acts vertically downward. A normal force acts from the ruler toward the marble/ball in a direction that is perpendicular to the plane of the ruler. Friction acts in the direction opposite to which the marble/ball is moving. Gravity keeps the marble/ball on the ruler as it also helps it accelerate down the ruler. The normal force pushes back on the marble/ball and, allowing it to roll smoothly down the ruler. Friction slows down the marble/ball.
- Distinguish between starting friction and rolling friction. Which is greater? Describe how each of these is involved in this experiment.
Answer: Starting friction is the friction that must be overcome to allow an object at rest to begin moving. It is greater than rolling friction, which is the friction that must be overcome to allow an object that is rolling to continue rolling. Starting friction was overcome to start the marble/ball rolling down the incline and rolling friction was overcome to keep it rolling down the incline.
- How does the height of the ramp affect the force the marble/ball exerts on the cup? Explain.
Answer: The taller the ramp, the greater the force exerted by the marble/ball. This is because it has more energy to transfer to the container.
- How does the mass of the marble/ball affect the force it exerts on the cup? Explain.
Answer: The greater the mass of the marble/ball, the greater the force it exerts on the container. This is because it has more energy to transfer to the container.
- How does the distance between the end of the ruler and the cup affect the force the marble/ball exerts on the cup? Explain.
Answer: If friction is neglected, there would be no change in the force. If friction is considered, the force would be weaker since the marble/ball would slow down and have less energy.
- What effect would using a gumball with the same volume but a smaller mass than the marble/ball have on your results? Explain.
Answer: The gumball would provide a smaller force on the storage container and the container would therefore move a smaller distance.
- How would your results change if the floor is carpeted? Explain.
Answer: There would be more friction. This would cause the marble/ball to slow down before contacting the storage container, thereby reducing the force it will exert.
- Describe how each of Newton’s Laws of Motion relates to this activity.
Answer: Newton’s 1st Law of motion relates to objects at rest or moving at a constant velocity due to balanced forces. This would apply to the marble/ball being at rest before it is released. If you neglect friction and consider the marble/ball to be moving at a constant velocity between the ramp and the container due to the smooth nature of the surface, it will apply to this situation as well. Newton’s 2nd Law relates to objects that are accelerating due to the presence of unbalanced forces. In this investigation, this occurs when the marble/ball accelerates down the incline, when it slows down due to friction (assuming the surface is not frictionless), when the container begins to move after being struck by the marble/ball as well as when it comes to a stop. Newton’s 3rd Law relates to the presence of equal and opposite forces. In this lab, it can be used to describe the interaction between the marble/ball and the surface it is in contact with and the interaction between the marble/ball and the storage container as they collide.
- If a force of 10 N is applied to 2.5 kg container, at what rate will the container accelerate?
Answer: 4 m/s2
- If a 10 N force causes a container to accelerate at a rate of 2 m/s2, what is the mass of the container?
Answer: 5 kg
- What force is needed to accelerate a 7.5 kg container at a rate of 6.0 m/s2?
Answer: 45 N
- How does the motion of the marble/ball change when it collides with the container? Explain. Which of Newton’s laws does this relate to?
Answer: The marble/ball reverses direction because the force the container exerts on the ball is opposite to the force the marble/ball exerts on the container. This relates to Newton’s 3rd Law.
- Describe the relationship that exists between force, mass, and acceleration. Which of Newton’s laws describes this?
Answer: Force is directly proportional to both mass and acceleration; mass is inversely proportional to acceleration. This is described by Newton’s 2nd Law.